Induction of apoptosis in HeLa cells via caspase activation by resveratrol and genistein

Selectively inducing apoptosis in cancer cells is a much desired strategy when tolerance toward side effects is minimal during chemotherapy. In our search for natural products that can induce apoptosis in human cervical cancer cells (HeLa), we selected resveratrol and genistein for our study. We conducted several experiments to test whether genistein can synergistically enhance the apoptotic potential of resveratrol at doses lower than the usual cytotoxic dose. Both resveratrol and genistein were able to induce apoptosis by enhancing the activities of caspase-9 and caspase-3 by themselves and also in combination. After 24 h of exposure to resveratrol and genistein, individually or in combination, lowered mitochondrial membrane potential was observed in HeLa cells. In addition, the mitochondrial membrane potential in HeLa cells was decreased, forcing JC-1 to stay in the monomeric form. The monomeric JC-1(5,5′,6,6′ -tetrachloro-1,1′,3,3′-tetraethyl benzimedazolyl carbocyanine iodide) emitted green fluorescence. In the control group, the color of the fluorescence was red due to aggregation of JC-1 in the physiological pH. The treatment groups exhibited DNA fragmentation as the hallmark of apoptotic nuclear features. We also detected an obvious decrease in the level of HDM2 gene expression after both individual and combination treatments with resveratrol and genistein. Our findings suggest that resveratrol and genistein when combined can induce apoptosis at doses lower than usual doses, through the activation of caspases cascade, and by decreasing the expression of HDM2.